The preparation of the substrate for enameling is critical for the quality of the finished article. With sheet steel and other rolled metals, cleaning is normally accomplished by spray washers and cleaning systems. However, with cast parts, and particularly with cast iron, blasting is the preferred method of surface treatment. The process of blasting requires well-designed equipment, an effective abrasive, and a transport system for the substrates for processing through the blasting machinery. A variety of machines have been designed for abrasive cleaning depending on the type of substrates to be processed. Small parts can be cleaned in batches in units that may be described as barrel units (Figure 1). Large parts can be cleaned in automated systems that may be continuous belts or conveyers traversing through blasting zones (Figure 2). Management of the abrasive is another important aspect of blasting operations. The size, distribution, hardness, and cleanliness of the abrasive have a significant effect on the efficiency of the blasting process. The roughness of the surface can be measured as shown in Figure 3 with surface finish data. A variety of mixes of abrasive are used to tailor the surface roughness (Figure 4).
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